Why animal magnetism is all about me, me, me

Animal issues are often headline news - Dolly, anti-hunting protests, the BSE crisis, animal rights activism, pigs' parts used in replacement surgery. But how rarely is critical thought given to our cultural relations to the animal kingdom at large. This should perhaps come as little surprise: today's urban society has so little contact with wildlife, and pets for their part have been granted too easy a familiarity: to confess to being an "animal lover" stills rather than spurs further questioning.

Few attempts have been made to survey the development of man's attitudes towards his fellow creatures. Certain dramatic climaxes to the story have attracted attention, of course - the flourishing Darwin industry has endlessly debated whether the Victorians preferred to be descended from apes or angels. But until now, few truly penetrating pieces of historical research have been devoted to the subject as a whole, Keith Thomas's pioneering Man and the Natural World (1983) and Harriet Ritvo's The Animal Estate: The English and Other Creatures in the Victorian Age (1987) being shining exceptions. We even lack a definitive history of pets.

Its title notwithstanding, Midas Dekkers's Dearest Pet , first published in Dutch in 1992, is not that, nor does it pretend to pass itself off as primary historical research. But its neatly inter-knitted essays, graced by unfamiliar and often stunning illustrations, does afford thoughtful insights into the spectrum of human beliefs, past and present, about our fellow living beings. Wearing his learning lightly, and adopting a wry style admirably captured by the translation, Dekkers, a biologist and broadcaster, addresses such questions as taxonomic idiosyncrasies and anomalies, and the comparative history of cross-breeding in actuality and mythology alike. Why does nature allow certain "mules" but not others? How radically would the living world be changed if it were largely populated by "geep" and their equivalents - what would happen if we really could not tell the sheep from the goats?

And why, for their part, have legends conjectured particular kinds of "monsters" and not others: what is the special magic of mermaids or wyverns? Was the centaur a product of the imagination of primitive peoples on first sighting mounted warriors, or is speculation of that kind fit only for the dustbin of learned ingenuity?

Dekkers probes into more philosophical and theological issues too. Given that "God's creation is a mess", what drove our ancestors to classify beasts in a rigidly hierarchical way in the Great Chain of Being? Why, taste and nutritional status apart, are certain animals judged fit for eating, while others are utterly taboo for the table? What logic lay behind the practice, so common in medieval Christendom, of subjecting damage-causing animals to formal legal proceedings, even execution? And on what grounds these days is cruelty to certain creatures (dogs and horses, for instance) an offence in the eyes of the law, whereas we westerners have traditionally assumed - Tristram Shandy's Uncle Toby notwithstanding - that flies may be swatted and "vermin" killed with total impunity?

As may already be sensed, Dekkers's inquiries address the visceral as much as the cerebral. Reasoning about animals involves rationalisation of feelings and prejudices whose logic is not always very obvious. Why, to take an example, do some creatures consistently top the lists of favourite pets?

The "cuddliness" explanation, so often given, is wanting - or rather is too narrowly reductionist. What truly appeal, suggests Dekkers, are humanoid traits, pandering to our narcissism, though animals approximate towards the anthropomorphic in more than one way. Some are two-legged (or almost so, like Dr Johnson's dog); some are particularly upright (penguins and owls get picked among the birds); some can look you in the eye; others, such as parrots, speak or can be trained like children.

Indeed, it seems to be the closeness to children that explains the frisson caused by the facet of our attitudes towards animals that gives Dekkers his subtitle. Why is it that bestiality conveys such a charge of the forbidden when (in rural societies at least) sex with animals is (as Kinsey documented) ubiquitous, and when fantasies of it filled the mythologising imagination: Leda and the swan, for instance, and all the other couplings of Zeus. Why was it that, in her early modern demonisation, the witch was accused not merely of wielding maleficium but of giving herself over to illicit sexual congress with her familiars?

These are big and often imponderable questions, and it is to Dekkers's credit that he does not claim to come up with final answers; the strength of his book lies primarily in its shrewd insights and felicitous examples. Thanks to this astute study, however, you will not be able to stroke your pet tortoise or tell your bedtime Aesop's fables without at least pausing for thought.

Roy Porter is professor in the social history of medicine, Wellcome Institute for the History of Medicine, London.